All images are 100% crops at the highest resolution JPEG setting on each camera, except the first image which shows the full scene in an image downsized in photoshop. The macros are also uncroped and downsized in photoshop, without sharpening.
Settings, auto mode all cameras. ASA 100 Canon Rebel XT. ASA 50 Panasonic. Image stabilization mode one on Panasonic, Paarameter one with sharpening at 1 plus (default) on EOS rebel XT.
Lens tested: Canon 70-200 2.8 USM IS L lens, Sigma 18-200, Canon kit lens 18-55 mm, and Canon 50mm 1.8 II (new series), and Panasonic built in Leica 6-72 mm F2.8 image stabiled lens.

Conclusion: The Canon L glass and Pansonic/Leica lens are of similar quality and far exceed the sigma superzoom or regular Canon glass. A head to head comparison of a $5400 Canon 20D outfit versus a Panasonic FZ30 was done, and the author felt it was a tie! http://www.firingsquad.com/hardware/panasonic_lumix_dmc-fz30_canon_eos-20d_camera_shootout/